1. Field of the Invention
This invention primarily relates to a probe, to an imaging device in which said probe is employed and to a method for the practical application of said device.
2. Description of the Prior Art
Various types of ultrasonic scanning probes are already known. A first known type consists of sector scanning probes or in other words probes provided either with an oscillating moving system or with a plurality of electroacoustic transducers mounted on a wheel and switched as they pass in front of an emission window. The properties of these probes lie in their high rate of acquisition and simplicity of design involving relatively simple and inexpensive signal-processing means. The coupling surface for acoustic waves is relatively small, thus making it possible to place the probe between two of the patient's ribs for cardiac observations. On the other hand, these probes have a service life of limited duration.
A second known type consists of a plurality of electroacoustic transducers. Those in common use include the linear-scan device in which provision is made for a linear strip consisting, for example, of 64 elementary electroacoustic transducers. Scanning is performed by displacing the group of active transducers at each shot or emission of ultrasound waves. This type of linear strip provides low resolution by reason of the small number of transducers employed simultaneously.
In the case of linear strips, when the beam is focused by electronic scanning and by making use of time-delays in order to compensate for path differences, the scanning angle is limited. Moreover, this solution is difficult to apply in practice as well as costly since it is necessary to have elements which induce substantial time-delays while maintaining coherence of the signal.
A tentative solution to these problems has been provided by convex strips, that is to say strips in which the transducer has been disposed on a curve and the radiating surface of which is convex. A strip of this type is described in particular in European patent No. 69,677. However, the resolution of a strip of this type is still not sufficient.
All the transducers of a strip of this type cannot insonate in all directions.